Libraries in TI-BASIC
by Aeromax

~~Say you have a long part of code you want to reference from other programs. You might include this code in the program itself, but say you need it to be used by a ton of programs. Like a time-delay sequence for games that (by definition) is going to be long as hell.

~~Now here all you really have to do is create a program with a good reference name (one which won't have to be changed later) and reference that program within other ones. Here's an example of a delay sequence being referenced by external programs.

PrgmFOOBAR
Lbl BG
Input "DELAY TIME: ",D
randInt(1,2)->A
If A=1
Disp "FOO"
If A=2
Disp "BAR"
Prgm DELAYSEQ
ClrHome
Disp "BAZBOP"

~~Let's go to the delay sequence program now.

PrgmDELAYSEQ
0->X
Repeat X=A
X+1->X
End

~~Now that's a good program, but can't be used in many programs. Why? Because it uses the common variable X. X gets used a lot, and its use in the delay sequence might overwrite another use of it (like the location of a cursor resetting to A every time you delay). Instead, let's use a list. There are infinite numbers of lists and it's highly unlikely that two would collide.

PrgmDELAYSEQ
0->LDELAY(1)
Repeat LDELAY(1)=A
LDELAY(1)+1->LDELAY(1)
End

~~Much better. But say we want to have it perform a function specific to this program. What to do? Well, we can put in a function switch. These are clunky, but they work well.

PrgmFOOBAR
Lbl BG
Input "DELAY TIME: ",D
randInt(1,2)->A
If A=1
Disp "FOO"
If A=2
Disp "BAR"
1->LDELAY(2)
Prgm DELAYSEQ
ClrHome
Disp "BAZBOP"

PrgmDELAYSEQ
2-> dim(LDELAY) ~~(this is necessary so it doesn't give a dimension error with the second element)
0->LDELAY(1)
Repeat LDELAY(1)=A
LDELAY(1)+1->LDELAY(1)
If LDELAY(2)=1
Then
Disp "HAM"
End
End

You can use control switches like this in a lot of places, not the least of all are subroutines in programs.